Courtesy App for Movie-Goers

I'll admit I'm not up to date on the permissions and capabilities of the latest Blackberry or iOS version (if they're up to spec, then this app is by all means for them, too), but on Android smartphones, there are apps available (free apps) which allow you to modify their behavior by texting a certain code to your smartphone. Behaviors that can be modified thusly include, but are not limited to, locking the screen, enabling the GPS chip, wiping all data from it, and overriding silent mode to increase the volume to max power and sound an alarm. The expected purpose of such apps is, of course, to help locate a lost/stolen phone, prevent its data from being accessed by anyone who finds it that isn't you, and destroying all data in the event that you've given up hope on ever finding it.

I have a different purpose in mind.

My idea is for an app (hopefully available cross-platform, but if iPhones must get left out because the designers don't want to play ball... well, that's a sacrifice I'm willing to make) which partners with movie theaters. When you buy tickets, you provide your phone number and, if you haven't already done so, download the app. At the time the movie is scheduled to start, or maybe 5-10 mins prior, a text is sent to your phone to activate the GPS, if it's not already activated. If it detects your phone is more than, say, 1/4 mile from the theater you are scheduled to be at, it triggers a loud chirp to get your attention, and displays an on-screen message reminding you about your movie appointment. If it detects that you are within 1/4 mile of the theater, it automatically silences the phone for you. At the time the movie ends, your phone receives another text code to re-enable the ringer so you don't forget.